/********************************************************
 *  ██████╗  ██████╗████████╗██╗
 * ██╔════╝ ██╔════╝╚══██╔══╝██║
 * ██║  ███╗██║        ██║   ██║
 * ██║   ██║██║        ██║   ██║
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 *  ╚═════╝  ╚═════╝   ╚═╝   ╚══════╝
 * Geophysical Computational Tools & Library (GCTL)
 *
 * Copyright (c) 2023  Yi Zhang (yizhang-geo@zju.edu.cn)
 *
 * GCTL is distributed under a dual licensing scheme. You can redistribute 
 * it and/or modify it under the terms of the GNU Lesser General Public 
 * License as published by the Free Software Foundation, either version 2 
 * of the License, or (at your option) any later version. You should have 
 * received a copy of the GNU Lesser General Public License along with this 
 * program. If not, see <http://www.gnu.org/licenses/>.
 * 
 * If the terms and conditions of the LGPL v.2. would prevent you from using 
 * the GCTL, please consider the option to obtain a commercial license for a 
 * fee. These licenses are offered by the GCTL's original author. As a rule, 
 * licenses are provided "as-is", unlimited in time for a one time fee. Please 
 * send corresponding requests to: yizhang-geo@zju.edu.cn. Please do not forget 
 * to include some description of your company and the realm of its activities. 
 * Also add information on how to contact you by electronic and paper mail.
 ******************************************************/

#include "gaussfunc.h"

gctl::gaussian_para1d::gaussian_para1d(){}

gctl::gaussian_para1d::gaussian_para1d(double in_mu, double in_sigma)
{
    if (in_sigma <= 0.0)
    {
        throw std::runtime_error("[GCTL] Invalid parameters for gctl::gaussian_para1d.");
    }

    mu = in_mu;
    sigma = in_sigma;
}

gctl::gaussian_para2d::gaussian_para2d(){}

gctl::gaussian_para2d::gaussian_para2d(double in_mux, double in_muy, double in_sigmax, 
    double in_sigmay, double in_rho)
{
    if (in_rho >= 1.0 || in_rho <= -1.0 ||  in_sigmax <= 0.0 || in_sigmay <= 0.0)
    {
        throw std::runtime_error("[GCTL] Invalid parameters for gctl::gaussian_para2d.");
    }

    mu_x = in_mux;
    mu_y = in_muy;
    sigma_x = in_sigmax;
    sigma_y = in_sigmay;
    rho = in_rho;
}

double gctl::gaussian_dist1d(double x, const gaussian_para1d &para, gradient_type_e mode)
{
    if (mode == Value) return exp(-1.0*(x-para.mu)*(x-para.mu)/(2.0*para.sigma*para.sigma))/(sqrt(2.0*M_PI)*para.sigma);
    if (mode == Dx) return -1.0*(x-para.mu)/(para.sigma*para.sigma)*exp(-1.0*(x-para.mu)*(x-para.mu)/(2.0*para.sigma*para.sigma))/(sqrt(2.0*M_PI)*para.sigma);

    throw std::invalid_argument("[GCTL] Invalid calculating type for gctl::gaussian_dist1d(...)");
}

double gctl::gaussian_dist2d(double x, double y, const gaussian_para2d &p, 
    gradient_type_e mode)
{
    double part = -0.5*(pow((x-p.mu_x)/p.sigma_x,2) -2*p.rho*(x-p.mu_x)*(y-p.mu_y)/(p.sigma_x*p.sigma_y)
        + pow((y-p.mu_y)/p.sigma_y,2)) / (1.0-p.rho*p.rho);

    double part2;
    if (mode == Value)
    {
        return exp(part)/(2*GCTL_Pi*p.sigma_x*p.sigma_y*sqrt(1-p.rho*p.rho));
    }
    
    if (mode == Dx)
    {
        part2 = -1.0*((x-p.mu_x)/(p.sigma_x*p.sigma_x) - p.rho*(y-p.mu_y)/(p.sigma_x*p.sigma_y))/(1.0-p.rho*p.rho);
        return part2*exp(part)/(2*GCTL_Pi*p.sigma_x*p.sigma_y*sqrt(1-p.rho*p.rho));
    }
    
    if (mode == Dy)
    {
        part2 = -1.0*((y-p.mu_y)/(p.sigma_y*p.sigma_y) - p.rho*(x-p.mu_x)/(p.sigma_x*p.sigma_y))/(1.0-p.rho*p.rho);
        return part2*exp(part)/(2*GCTL_Pi*p.sigma_x*p.sigma_y*sqrt(1-p.rho*p.rho));
    }

    throw std::invalid_argument("[GCTL] Invalid calculating type for gctl::gaussian_dist2d(...)");
}